powerpc/papr_scm: Update the NUMA distance table for the target node

Platform device helper routines won't update the NUMA distance table
while creating a platform device, even if the device is present on a
NUMA node that doesn't have memory or CPU. This is especially true for
pmem devices. If the target node of the pmem device is not online, we
find the nearest online node to the device and associate the pmem device
with that online node. To find the nearest online node, we should have
the numa distance table updated correctly. Update the distance
information during the device probe.

For a papr scm device on NUMA node 3 distance_lookup_table value for
distance_ref_points_depth = 2 before and after fix is below:

Before fix:
  node 3 distance depth 0  - 0
  node 3 distance depth 1  - 0
  node 4 distance depth 0  - 4
  node 4 distance depth 1  - 2
  node 5 distance depth 0  - 5
  node 5 distance depth 1  - 1

After fix
  node 3 distance depth 0  - 3
  node 3 distance depth 1  - 1
  node 4 distance depth 0  - 4
  node 4 distance depth 1  - 2
  node 5 distance depth 0  - 5
  node 5 distance depth 1  - 1

Without the fix, the nearest numa node to the pmem device (NUMA node 3)
will be picked as 4. After the fix, we get the correct numa node which
is 5.

Fixes: da1115fdbd6e ("powerpc/nvdimm: Pick nearby online node if the device node is not online")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230404041433.1781804-1-aneesh.kumar@linux.ibm.com

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index b44ce71917d75a9668d42e0fe6fe328e653a2790..16cfe56be05bb28723a065daf1dbf2de91d29aac 100644 (file)
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -366,6 +366,7 @@ void update_numa_distance(struct device_node *node)
        WARN(numa_distance_table[nid][nid] == -1,
             "NUMA distance details for node %d not provided\n", nid);
 }
+EXPORT_SYMBOL_GPL(update_numa_distance);
 
 /*
  * ibm,numa-lookup-index-table= {N, domainid1, domainid2, ..... domainidN}

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 2f8385523a1320047925af07a7219618a48c60d5..1a53e048ceb768f175237361018d6177092b4220 100644 (file)
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -1428,6 +1428,13 @@ static int papr_scm_probe(struct platform_device *pdev)
                return -ENODEV;
        }
 
+       /*
+        * open firmware platform device create won't update the NUMA 
+        * distance table. For PAPR SCM devices we use numa_map_to_online_node()
+        * to find the nearest online NUMA node and that requires correct
+        * distance table information.
+        */
+       update_numa_distance(dn);
 
        p = kzalloc(sizeof(*p), GFP_KERNEL);
        if (!p)